so...
lightsabres?
also what you've described is basically a weapon that would function as the perfect rapier: great tip control but 0 slashing power.
if the arcanist blade was heavy "because of the hilt" then it would have very little mass in the blade, making it a quite shitty cutting weapon.
in order to create a fairly well-balanced weapon the magic would have to be of a weight comparable to the hilt, but overall this weapon would probably end up way lighter than a normal sword, for all that entails